Polymorphs of Brimonidine Pamoate

ABSTRACT

A brimonidine pamoate polymorph exhibits characteristics disclosed herein. The polymorph is included in a composition, device, or implant for use in the treatment or control of elevated intraocular pressure or in the neuroprotection of components of a neurological tissue to prevent progressive degeneration of such components. In particular, such a composition, device, or implant can be used to provide neuroprotection to cells and components of the optic nerve system.

CROSS-REFERENCE

This application is a divisional of patent application Ser. No.12/604,427, filed Oct. 23, 2009, which application claims the benefit ofProvisional Patent Application No. 61/115,711 filed Nov. 18, 2008, bothof which are incorporated by reference herein.

BACKGROUND OF THE INVENTION

The present invention relates to polymorphs of brimonidine pamoate,compositions comprising such polymorphs, and methods of treating orcontrolling diseases using such polymorphs. In particular, the presentinvention relates to stable polymorphs of brimonidine pamoate and suchcompositions comprising such polymorphs for sustained release thereof.

Polymorphism is a property of a substance to exist in more than onesolid state crystal structures. The various polymorphicforms—polymorphs—of a crystal have different crystal lattices and,thereby, different physical and chemical properties, such as density,hardness, chemical stability, solubility, rate of dissolution indifferent solvents, melting point, phase transformation, hygroscopicity,interactions with biological systems, etc. In addition, the term“pseudopolymorphisms” has been applied to different hydrates andsolvates of a crystalline material in which water or solvent moleculeshave been built into the crystal lattice.

Brimonidine, 5-bromo-6-(2-imidazolidinylideneamino)quinoxaline (Formula1), is an α₂ selective adrenergic receptor agonist that has been used inthe treatment of open-angle glaucoma by decreasing aqueous humorproduction and increasing uveoscleral outflow.

For this use, topical ophthalmic solutions have been formulated and thetartrate salt of brimonidine has been used to provide increasedsolubility of brimonidine. The solubility of brimonidine tartrate is 34mg/mL in water, and 2.4 mg/mL in a pH 7.0 phosphate buffer while thesolubility of brimonidine freebase is negligible in water (see; e.g.,U.S. Patent Application Publication 2006/0257452).

Recent studies suggested that brimonidine eye drops may have aneuroprotective effect in a rodent model of ischemic-induced optic nervecell death. N. O. Danylkova et al., Exp. Eye Res., Vol. 84, 293 (2007);M. P. Lafuente et al., Exp. Eye Res., Vol. 74, 1981 (2002). However,topical application of brimonidine may not be the most effective mannerto provide therapeutic effect to neurological tissues in the back of theeye because of the rapid clearance of topically applied compositions.

Intravitreal delivery of brimonidine can provide better access of thedrug to the tissues in the back of the eye. Such delivery can beachieved by injecting a liquid-containing composition into the vitreous,or by placing polymeric drug delivery systems, such as implants andmicroparticles, into the vitreous. Examples of biocompatible implantsfor placement in the eye have been disclosed in a number of patents,such as U.S. Pat. Nos. 4,521,210; 4,853,224; 4,997,652; 5,164,188;5,443,505; 5,501,856; 5,766,242; 5,824,072; 5,869,079; 6,074,661;6,331,313; 6,369,116; and 6,699,493. However, intravitrealadministration of drugs should be as infrequent as possible to avoidunnecessary disturbance of the eye.

Therefore, it is very desirable to provide stable brimonidine salts forthe preparation of sustained-release compositions. It is also verydesirable to provide brimonidine salts that are stable in the vitreoushumor. In addition, it is also very desirable to provide suchbrimonidine salts for duration in ocular environments where they canprovide effective neuroprotection to the optic nerve system.

SUMMARY

In general, the present invention provides polymorphs of brimonidinepamoate.

In one aspect, the present invention provides stable or substantiallystable polymorphs of brimonidine pamoate.

In another aspect, the present invention provides thermodynamicallystable brimonidine pamoate polymorphs.

In another aspect, the present invention provides at least polymorphicforms A, B, C, D, E, and F (as designated herein) of brimonidinepamoate, each having distinguishing characteristics disclosed herein.

In still another aspect, the present invention provides brimonidinepamoate polymorph Form F characterized by an X-ray powder diffraction(“XRPD”) spectrum that comprises peaks at 2θ angles of 7.1, 9.8, 17.8,and 25.5°±0.2°.

In yet another aspect, the present invention provides brimonidinepamoate polymorph Form F characterized by a Raman spectroscopy spectrumthat comprises peaks at 145.1, 156.3, 1336.8, 1364.4, and 1412.5 cm⁻¹.

In a further aspect, the present invention provides brimonidine pamoatepolymorph Form E characterized by an XRPD spectrum that comprises peaksat 2θ angles of 7.7, 8.0, 13.1, and 21.2°±0.2°.

In yet another aspect, the present invention provides brimonidinepamoate polymorph Form E characterized by a Raman spectroscopy spectrumthat comprises peaks at 1339.9, 1368.7, 1396.1, 1403.1, and 1410.8 cm⁻¹.

In still another aspect, the present invention provides brimonidinepamoate polymorph Form B characterized by an XRPD spectrum thatcomprises peaks at 2θ angles of 9.7, 14.6, 25.9, and 26.5°±0.2°.

In yet another aspect, the present invention provides brimonidinepamoate polymorph Form B characterized by a Raman spectroscopy spectrumthat comprises peaks at 1335.6, 1364.6, 1404.4, 1410.7, and 1462.1 cm⁻¹.

In still another aspect, the present invention provides brimonidinepamoate polymorph Form C characterized by an XRPD spectrum thatcomprises peaks at 2θ angles of 7.7, 12.8, 13.4, and 23.8°±0.2°.

In yet another aspect, the present invention provides brimonidinepamoate polymorph Form C characterized by a Raman spectroscopy spectrumthat comprises peaks at 161.5, 1344.8, 1354.1, 1367.9, and 1402.2 cm⁻¹.

In still another aspect, the present invention provides brimonidinepamoate polymorph Form D characterized by an XRPD spectrum thatcomprises peaks at 2θ angles of 7.5, 12.8, 24.5, and 27.1°±0.2°.

In yet another aspect, the present invention provides brimonidinepamoate polymorph Form D characterized by a Raman spectroscopy spectrumthat comprises peaks at 157.4, 1270.4, 1341.5, 1355.5, and 1403.0 cm⁻¹.

In still another aspect, the present invention provides brimonidinepamoate polymorph Form A characterized by an XRPD spectrum thatcomprises peaks at 2θ angles of 13.5, 20.6, 21.1, and 24.4°±0.2°.

In yet another aspect, the present invention provides brimonidinepamoate polymorph Form A characterized by Raman spectroscopy spectrumthat comprises peaks at 1340.8, 1352.4, 1365.8, 1402.0, and 1460.3 cm⁻¹.

In still another aspect, the present invention provides a pharmaceuticalcomposition comprising a polymorph of brimonidine pamoate selected fromthe group consisting of polymorph Forms A, B, C, D, E, F, andcombinations thereof.

In still another aspect, the present invention provides a pharmaceuticalcomposition comprising a polymorph of brimonidine pamoate selected fromthe group consisting of polymorph Forms B, C, D, E, F, and combinationsthereof.

In a further aspect, the present invention provides a method fortreating or controlling glaucoma in a subject. The method comprisesadministering to an ocular environment of the subject a composition thatcomprises at least a polymorph of brimonidine pamoate selected from thegroup consisting of brimonidine pamoate polymorph Forms A, B, C, D, E,F, and combinations thereof. In one embodiment, said treating orcontrolling is effected by reducing intraocular pressure (“IOP”) in anaffected eye of said subject.

In still another aspect, the present invention provides a method foreffecting ocular neuroprotection in a subject. The method comprisesadministering to an ocular environment of the subject a composition thatcomprises at least a polymorph of brimonidine pamoate selected from thegroup consisting of brimonidine pamoate polymorph Forms A, B, C, D, E,F, and combinations thereof. In one embodiment, said composition isadministered into a posterior segment of an eye of the subject in needof said neuroprotection.

Other features and advantages of the present invention will becomeapparent from the following detailed description and claims and theappended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an XRPD spectrum of brimonidine pamoate polymorph Form A.

FIG. 2 shows an ¹H NMR spectrum of brimonidine pamoate polymorph Form A.

FIG. 3 shows a DSC curve of brimonidine pamoate polymorph Form A.

FIG. 4 shows a TGA curve of brimonidine pamoate polymorph Form A.

FIG. 5 shows a Raman spectroscopy spectrum of brimonidine pamoatepolymorph Form A.

FIG. 6 shows An XRPD stack plot of brimonidine hemi-pamoate competitiveslurry samples (a) starting material, lot SUC-I-130(1), Form A, (b) lotSUC-I-133(37), Form F, (c) lot SUC-I-138(1), isolated following one weekof Forms A, C, D and E slurry in water, (d) lot SUC-I-132(2), Form E,and (e) lot SUC-I-138(2) isolated following one week of Forms A, B, Cand D slurry in THF. Patterns (c) and (e) were found to be consistentwith patterns (b) and (d), Forms F and E respectively.

FIG. 7 shows an XRPD spectrum of brimonidine pamoate polymorph Form B.

FIG. 8 shows an ¹H NMR spectrum of brimonidine pamoate polymorph Form B.

FIG. 9 shows a DSC curve of brimonidine pamoate polymorph Form B.

FIG. 10 shows a TGA curve of brimonidine pamoate polymorph Form B.

FIG. 11 shows a Raman spectroscopy spectrum of brimonidine pamoatepolymorph Form B.

FIG. 12 shows an XRPD spectrum of brimonidine pamoate polymorph Form C.

FIG. 13 shows an ¹H NMR spectrum of brimonidine pamoate polymorph FormC.

FIG. 14 shows a DSC curve of brimonidine pamoate polymorph Form C.

FIG. 15 shows a TGA curve of brimonidine pamoate polymorph Form C.

FIG. 16 shows a Raman spectroscopy spectrum of brimonidine pamoatepolymorph Form C.

FIG. 17 shows an XRPD spectrum of brimonidine pamoate polymorph Form D.

FIG. 18 shows an ¹H NMR spectrum of brimonidine pamoate polymorph FormD.

FIG. 19 shows a DSC curve of brimonidine pamoate polymorph Form D.

FIG. 20 shows a TGA curve of brimonidine pamoate polymorph Form D.

FIG. 21 shows a Raman spectroscopy spectrum of brimonidine pamoatepolymorph Form D.

FIG. 22 shows an XRPD spectrum of brimonidine pamoate polymorph Form E.

FIG. 23 shows an ¹H NMR spectrum of brimonidine pamoate polymorph FormE.

FIG. 24 shows a DSC curve of brimonidine pamoate polymorph Form E.

FIG. 25 shows a TGA curve of brimonidine pamoate polymorph Form E.

FIG. 26 shows a Raman spectroscopy spectrum of brimonidine pamoatepolymorph Form E.

FIG. 27 shows an XRPD spectrum of brimonidine pamoate polymorph Form F.

FIG. 28 shows an ¹H NMR spectrum of brimonidine pamoate polymorph FormF.

FIG. 29 shows a DSC curve of brimonidine pamoate polymorph Form F.

FIG. 30 shows a TGA curve of brimonidine pamoate polymorph Form F.

FIG. 31 shows a Raman spectroscopy spectrum of brimonidine pamoatepolymorph Form F.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the term “control” also includes reduction, alleviation,amelioration, and prevention.

As used herein, the term “stable” means incapable of changing incrystalline structure, as exhibited by a plurality of peaks in an XRPDpattern, at a time of two weeks after the initial preparation of thematerial.

As used herein, the term “neuroprotection” means the rescue of at leastsome cells or components of a nervous system that are not directlydamaged by the primary cause of a disease or injury, but would otherwiseundergo secondary degeneration without therapeutic intervention. In oneaspect, neuroprotection can lead to preservation of the physiologicalfunction of these cells or components. In one aspect, such a nervoussystem is the optic nerve system. The cells or components of the opticnerve system include those being involved or assisting in conversion ofphoton to neurological signals and the transmission thereof from theretina to the brain for processing. Thus, the main cells or componentsof the optic nerve system include, but are not limited to, pigmentepithelial cells, photoreceptor cells (rod and cone cells), bipolarcells, horizontal cells, amacrine cells, interplexiform cells, ganglioncells, support cells to ganglion cells, and optic nerve fibers.

In general, the present invention provides polymorphs of brimonidinepamoate.

In one aspect, such polymorphs comprise stable or substantially stablebrimonidine pamoate polymorphs.

In another aspect, the present invention provides thermodynamicallystable brimonidine pamoate polymorphs.

In still another aspect, the present invention provides at leastpolymorphic forms A, B, C, D, E, and F (as designated herein) ofbrimonidine pamoate, each having distinguishing characteristicsdisclosed herein.

In yet another aspect, the present invention provides at leastpolymorphic forms B, C, D, E, and F of brimonidine pamoate, each havingdistinguishing characteristics disclosed herein.

Brimonidine Pamoate Polymorph Form A

In a 5 L 3-neck round bottom flask equipped with overhead stirrer,heating mantle, condenser, temperature probe, and N₂ inlet, 4.8 g ofbrimonidine (lot 1-080085) was dissolved in ethanol (2000 mL) at 65° C.Pamoic acid (1.05 eq, 19.0 mL, 0.5M in DMSO (dimethyl sulfoxide)) wasthen added. The resulting solution was stirred for 30 minutes at 65° C.and then cooled at 20° C./hour to ambient temperature. At the onset ofthe cooling profile, precipitation of solids was observed. The mixturestirred overnight at ambient temperature and was then filtered. Theresulting solids were dried under vacuum at ambient temperature for 4days before being analyzed by XRPD to confirm the solid form, designatedas Form A. FIG. 1 shows an XRPD spectrum of brimonidine pamoatepolymorph Form A (lot SUC-I-130(1)).

In one aspect, polymorph Form A is characterized by an XRPD spectrumcomprising major peaks at 2θ angles of 13.5, 20.6, 21.1, and 24.4°±0.2°.

In another aspect, polymorph Form A is characterized by an XRPD spectrumcomprising peaks at 2θ angles of 7.6, 12.2, 12.7, 13.5, 20.6, 21.1,24.4, 26.5, and 27.7°±0.2°.

¹H NMR analysis of this material showed approximately 3.7 wt % residualethanol and a 0.5:1 pamoate to brimonidine ratio confirming theformation of a hemi-pamoate salt of brimonidine. FIG. 2 shows an NMRspectrum for brimonidine pamoate polymorph Form A (lot SUC-I-130(1).

Thermal analysis of Form A showed a single DSC endotherm at 221° C. (seeFIG. 3) attributed to the melting of the salt and 3.5 TGA weight lossthrough 190° C. (see FIG. 4) attributed to the removal of ethanol.

FIG. 5 shows a Raman spectroscopy spectrum of Form A (lot SUC-I-130(1),to be compared to Raman spectra of other polymorphs.

In one aspect, polymorph Form A is characterized by a Raman spectroscopyspectrum comprising major peaks at 1340.8, 1352.4, 1365.8, 1402.0, and1460.3 cm⁻¹.

In another aspect, polymorph Form A is characterized by a Ramanspectroscopy spectrum comprising peaks at 135.4, 169.3, 189.2, 233.0,326.9, 547.9, 693.3, 719.4, 838.3, 938.3, 1031.1, 1197.6, 1252.4,1270.2, 1340.8, 1352.4, 1365.8, 1402.0, 1460.3, 1549.0, 1556.0, and1571.0 cm⁻¹.

Moisture sorption analysis of Form A showed this hemi-pamoate polymorphto be slightly hygroscopic, adsorbing 2.2 percent by weight (“wt %”)water at 60 percent relative humidity (“% RH”) and 2.5 wt % water at 90%RH. Upon desorption, no hysteresis or indication of hydrate formationwas observed. XRPD analysis of the solids following moisture sorptionanalysis afforded a diffraction pattern which was consistent with theForm A starting material, indicating no polymorphic form conversion hadoccurred during the experiment.

Slurries of Form A were prepared in MeOH (methanol), THF(tetrahydrofuran), MIBK (methyl isobutyl ketone), toluene, water andEtOH (ethanol) as described below in an attempt to determine propensityof Form A to undergo form conversion in different solvent systems, asfollows. Approximately 15-30 mg of brimonidine hemi-pamoate Form A wasweighed into a 1 dram vial and 1.0 mL of solvent (MeOH, THF, MIBK,toluene, water, or EtOH) was added to each vial and allowed to stirmagnetically at ambient conditions for three weeks (see summary resultsin Table 1). Following one week intervals, samples were isolated bycentrifugation and dried in vacuo at ambient temperature overnight andanalyzed by XRPD to check for polymorphic form conversion.

TABLE 1 Summary of Three Weeks Slurry Experiments Hemi- Form Form FormHemi- Pamoate by by by Pamoate seeds Primary XRPD XRPD XRPD (Form A)(Form B) Solvent Temperature (1 (2 (3 Lot No. (mg) (mg) (mL) (° C.)week) weeks) weeks) SUC-I- 32.60 — MeOH 1 Ambient A A A 132(1) SUC-I-31.40 — THF 1 Ambient E E E 132(2) SUC-I- 33.30 — MIBK 1 Ambient A A A132(3) SUC-I- 32.30 — Toluene 1 Ambient A A A 132(4) SUC-I- 34.20 —Water 1 Ambient A A B 132(5) (magnetic stirring) SUC-I- 33.18 — EtOH 1Ambient A A A 132(6) SUC-I- 37.40 — Water 1 Ambient A A n/a 132(7)(Shaker) SUC-I- 14.9 1.4 Water 1 Ambient B B n/a 132(8) n/a - Sample notanalyzed

Solids isolated from a slurry of Form A in THF (lot SUC-I-132(2))following one week of equilibration, afforded a unique XRPD patterncompared to the diffraction patterns of Forms A, B, C, D and F. Furthercharacterization of this unique crystalline solid, designated as Form E,is detailed herein below. These findings indicate that Form E is morestable in THF than Form A. XRPD analysis of solids isolated from aslurry of Form A in water (lot SUC-I-132(5)) following three weeks ofequilibration showed conversion to Form B. These findings suggest thatForm B is more stable in water than Form A. Form A was also observed toconvert to Form B during the aqueous solubility experiment afterovernight equilibration in water. As a result, the aqueous solubility ofForm A was not determined. No form conversion was observed in theremaining slurry solvents as shown in Table 1.

In an effort to elucidate the relative thermodynamic stability of Form Awith respect to the other crystalline forms, competitive slurryexperiments were performed as follows. Approximately 15 mg ofbrimonidine hemi-pamoate Form A and 3 mg of either Forms B, C, D and Ewere weighed into a 1-dram vial and 1.0 mL of solvent (water or THF) wasadded (Table 2). Following one week of stirring at ambient conditions,the samples were isolated by centrifugation and dried in vacuo atambient temperature overnight at 30 inches of Hg. After drying, thesamples were analyzed by XRPD to check for form conversion. A one-weekslurry comprising Forms A, B, C and D in THF revealed that Form A willconvert to the most stable anhydrate form (Form E) as shown in FIG. 6.These findings are consistent with results obtained from the 1 weekslurry of Form A in THF Slurries comprising Forms A, C, D and E in watershowed conversion to Form F after one week of equilibration (Table 2).These results indicate that Form F, like Form B, is also relativelystable in water.

TABLE 2 Competitive Slurries of Brimonidine Hemi-Pamoate Forms Weight(mg) SUC-I- SUC-I- 130(1) 132(8) SUC-I- SUC-I- SUC-I- (Form (Form134(37) 134(25) 132(2) Solvent Temp XRPD Lo No. A) B) (Form C) (Form D)(Form E) (mL) (° C.) (1 week) SUC-I- 15.903 — 3.331 3.432 3.501 Water RTCrystalline 138(1) (1.0) (Form F) SUC-I- 16.559 3.373 3.819 3.237 — THFRT Crystalline 138(2) (1.0) (Form E)

The solid state stability of different polymorphs was assessed atelevated temperature and humidity as follows.

Elevated Temperature Stability

Approximately 3-5 mg of brimonidine hemi-pamoate Form A, B, C, D, or Ewere weighed into individual 1-dram vials and stored uncapped at 60° C.After one week of exposure, the samples were analyzed by XRPD to checkfor form conversion and HPLC analysis to check for potentialdegradation. After one week of storage at 60° C., Form A was observed tobe stable by XRPD and HPLC (Table 3).

Elevated Humidity Stability

Approximately 1-10 mg of brimonidine hemi-pamoate Form A, F, or C weretransferred to vial caps (uncapped) and stored in a closed containerwith saturated barium chloride dihydrate (BaCl₂.2H₂O). This solutionresults in 88% RH environment. After two weeks of storage thecrystalline form was determined by XRPD and solid inspected fordeliquescence. Forms A, C, and F were observed to be stable after twoweeks of storage at elevated relative humidity (88% RH), showing no signof deliquescence or change in crystalline form by XRPD (Table 4).

TABLE 3 Thermal Stress Study of Brimonidine Hemi-Pamoate Forms StartingHPLC Material Weight Temp. XRPD (% Lot No. Lot (Form) (mg) (° C.) (1week) purity) SUC-I- SUC-I-130(1) ~3-5 60 Crystalline 100.0 138(3) (FormA) (Form A) SUC-I- SUC-I-132(8) ~3-5 60 Crystalline 100.0 138(4) (FormB) (Form B) SUC-I- SUC-I-133(13) ~3-5 60 Semi-cryst. 97.9 138(5) (FormC) (Form C) SUC-I- SUC-I-134(7) ~3-5 60 Crystalline 96.7 138(6) (Form D)(Form D) ¹SUC-I- SUC-I-138(2) ~3-5 60 Semi-cryst. 100.0 138(7) (Form E)(Form E) ¹Sample exposed to elevated conditions for 6 days

TABLE 4 Humidity Chamber Study of Brimonidine Hemi-Pamoate FormsStarting Form by Visual Material Initial XRPD inspection NB Code Lot(s)(mg) % RH Form (2 week) (2 week) SUC-I-136(1) SUC-I-130(1) 88 A A Nodeli- (25.22) quescence SUC-I-136(2) SUC-I-133(37) F F No deli-SUC-I-133(38) quescence (4.3) SUC-I-136(3) SUC-I-133(34) C C No deli-(7.4) quescence

Brimonidine Pamoate Polymorph Form B

Form B was identified at first from a two-week slurry of Form A inwater. In addition, Form B was also observed from slow- and fast-cooling(see procedures disclosed below) crystallizations of Form A in DMF/waterbinary solvent. Form B was fully characterized as described below. FIG.7 shows an XRPD spectrum of Form B (lot SUC-I-133(36)).

Fast-Cooling Profile

Approximately 20-30 mg of brimonidine hemi-pamoate (lot SUC-I-130(1),Form A) was weighed to a 2-dram glass vial equipped with a stir bar. Thestarting material was dissolved in a minimal amount (typically 1-7 mL,depending on the ability of the solvent to dissolve the starting solid)of primary solvent at about 55° C. Each solution was passed through a0.45 μm syringe filter into a preheated vial to remove any undissolvedstarting material. Following the polish filtration the vials were placedin a refrigerator to achieve a fast cooling rate and left to equilibrateovernight. The following day, the vials were visually inspected forprecipitation; those vials with little to no precipitation were gentlyscratched with a metal spatula to facilitate crystal growth and thenallowed to equilibrate an additional 24 hours at 4° C. The resultantsolids were either isolated by vacuum filtration or in instances of noprecipitation were evaporated to dryness under a gentle stream ofnitrogen. All samples were then dried overnight in vacuo at ambienttemperature and analyzed by XRPD to determine the solid form.

Slow-Cooling Profile

Approximately 20-30 mg of brimonidine hemi-pamoate (lot SUC-I-130(1),Form A) was weighed to a 2-dram glass vial equipped with a stir bar. Thestarting material was dissolved in a minimal amount of primary solventat about 55° C. Each solution was passed through a 0.45 μm syringefilter into a preheated vial to remove any undissolved startingmaterial. Following the polish filtration the samples were cooled toambient temperature at the rate of 20° C./hour and also allowed toequilibrate overnight. The following day, the vials were visuallyinspected for precipitation; those vials with little to no precipitationwere gently scratched with a metal spatula to facilitate crystal growthand then allowed to equilibrate an additional 24 hours at ambienttemperature. The resultant solids were either isolated by vacuumfiltration or in instances of no precipitation were evaporated todryness under a gentle stream of nitrogen. All samples were then driedovernight in vacuo at ambient temperature and analyzed by XRPD todetermine the solid form.

In one aspect, polymorph Form B is characterized by an XRPD spectrumcomprising major peaks at 2θ angles of 9.7, 14.6, 25.9, and 26.5°±0.2°.

In another aspect, polymorph Form B is characterized by an XRPD spectrumcomprising peaks at 2θ angles of 7.0, 9.7, 10.9, 14.6, 19.0, 20.1, 23.4,25.9, 26.5, and 27.7°±0.2°

¹H NMR analysis showed a 0.5:1 pamoate to brimonidine ratio confirmingthe formation of a hemi-pamoate salt of brimonidine with approximately0.1 wt % residual DMF present. FIG. 8 shows an NMR spectrum forbrimonidine pamoate polymorph Form B (lot SUC-I-133(36)).

Thermal analysis of Form B showed DSC endothermic events at 76 and 225°C. (see FIG. 9) attributed to loss of residual solvent and melting ofthe crystalline salt. TGA analysis showed approximately 4.4% weight lossbetween 50 and 90° C. (see FIG. 10) likely attributed to the loss ofwater. Karl Fischer analysis of Form B showed 7.2 wt % water. Furthercharacterization by Raman spectroscopy showed major spectral differencescompared to anhydrate Forms A, C, D and E while only minor differenceswere observed compared to Form F. Thus, Form A slowly changed to Form Bupon contacting water.

Moisture sorption analysis of lot SUC-I-134(36) showed that Form Badsorbed 5.4 wt % water at 60% RH and 5.8 wt % water at 90% RH. Thewater content stabilized at around 5-6 wt % between 20-90% RH,coinciding with a sesqui-hydrate of brimonidine hemi-pamoate which wouldtheoretically contain 5.4 wt % water. XRPD analysis of the dried solidsfollowing the experiment afforded a diffraction pattern which wasconsistent with Form B, indicating that the dehydrated material hadconverted back to Form B upon exposure to ambient conditions.

FIG. 11 shows a Raman spectroscopy spectrum of Form B (lotSUC-I-132(8)).

In one aspect, the present invention provides brimonidine pamoatepolymorph Form B characterized by a Raman spectroscopy spectrum thatcomprises peaks at 1335.6, 1364.6, 1404.4, 1410.7, and 1462.1 cm⁻¹.

In another aspect, the present invention provides brimonidine pamoatepolymorph Form B characterized by a Raman spectroscopy spectrum thatcomprises peaks at 106.9, 176.5, 235.4, 379.3, 431.1, 553.6, 694.6,719.0, 1031.6, 1265.9, 1335.6, 1364.6, 1404.4, 1410.7, 1462.1, and1579.0 cm⁻¹.

A competitive slurry of Forms (A, B, C and D) in THF revealed that alongwith the other starting forms, Form B also converted to Form E after oneweek of equilibration. Form B was observed to be relatively stable inwater. This crystalline solid was isolated from a water slurry of Form Aafter 3 weeks and a mixture of Forms A and B after 1 week (Table 1).Form B was also observed during the aqueous solubility experimentfollowing an overnight slurry of Form A in water (Table 2). Thesolubility of Form B was determined to be in the range of 0.005-0.02mg/mL by HPLC. Mixtures of Forms B and Form F were also observed duringthe solubility experiments from individual slurries of Forms F, C, D andE. A competitive water slurry of Forms A, C, D, and E showed conversionto Form F (Table 2). Subsequent slurry studies demonstrated that aqueousslurries of mixtures of Form B and Form F always resulted in Form Bafter 7 or 14 days at either 40° C. or room temperature. Thus, Form B isthe more stable polymorph in water of the two, both of which are morestable in water than any of the other polymorphs.

Form B was observed to be stable in the solid state after 1 week ofstorage at 60° C. HPLC and XRPD analysis of the thermally stressedmaterial showed no degradation or signs of form conversion (Table 3).

Brimonidine Pamoate Polymorph Form C

Form C was observed from crystallizations of Form A in binary solventsystems, utilizing the fast cooling profile (disclosed herein above),such as: DMSO/MIBK, NMP (N-methyl-2-pyrrolidone)/acetone, NMP/MTBE(methyl-tert-butyl ether), NMP/EtOH, DMSO/IPAc (isopropyl acetate),NMP/IPA (isopropyl alcohol), and NMP/toluene. Form C was also observedfrom: NMP/MTBE, DMSO/EtOH, NMP/IPAc, DMSO/IPA, NMP/heptane, NMP/DCM(dichloromethane), NMP/toluene, NMP/water, NMP/THF and NMP/MeOH with aslow cooling profile. This unique solid was fully characterized asdescribed below.

Form C, lot SUC-I-133(34), afforded a unique crystalline XRPD patterncompared to the diffraction patterns of Forms A, B, D, E, and F. FIG. 12shows an XRPD spectrum of Form C (lot SUC-I-133(34)).

In one aspect, the present invention provides brimonidine pamoatepolymorph Form C characterized by an XRPD spectrum that comprises peaksat 2θ angles of 7.7, 12.8, 13.4, and 23.8°±0.2°.

In another aspect, the present invention provides brimonidine pamoatepolymorph Form C characterized by an XRPD spectrum that comprises peaksat 2θ angles of 7.7, 12.8, 13.4, 18.4, 19.2, 19.8, 22.6, and 23.8°±0.2°.

¹H NMR analysis of this material showed approximately 9.9 wt % residualNMP and a 0.5:1 pamoate to brimonidine ratio confirming the formation ofa hemi-pamoate salt of brimonidine. FIG. 13 shows an NMR spectrum forbrimonidine pamoate polymorph Form C (lot SUC-I-133(34)).

Thermal analysis of Form C showed a single DSC endothermic event at 210°C. (see FIG. 14) attributed to melting of the crystalline salt. Furtheranalysis by TGA showed weight loss of 6.4% between 50 and 140° C. (seeFIG. 15) likely due to the loss of water and approximately 7.2 wt % from180-230° C. (see FIG. 15) attributed to the loss of NMP.

FIG. 16 shows a Raman spectroscopy spectrum of Form C (lotSUC-I-133(25)).

In one aspect, the present invention provides brimonidine pamoatepolymorph Form C characterized by a Raman spectroscopy spectrum thatcomprises peaks at 161.5, 1344.8, 1354.1, 1367.9, and 1402.2 cm⁻¹.

In another aspect, the present invention provides brimonidine pamoatepolymorph Form C characterized by a Raman spectroscopy spectrum thatcomprises peaks at 135.8, 161.5, 428.7, 720.1, 1031.2, 1270.6, 1344.8,1354.1, 1367.9, 1402.2, 1461.1, 1549.5, and 1572.7 cm⁻¹.

Raman spectroscopy analysis of Form C showed minor spectral differencesin comparison to the Raman spectra of Forms A, D, and E, but significantdifferences in comparison to the spectra of Forms B and F in the rangeof about 1300-1425 cm⁻¹.

Moisture sorption analysis of lot SUC-I-134(37) showed the hemi-pamoateto be moderately hygroscopic, adsorbing 4.6 wt % water at 60% RH and13.0 wt % water at 90% RH. Upon desorption, no hysteresis or indicationof hydrate formation was observed. XRPD analysis of the solids followingthe experiment afforded a diffraction pattern which was consistent withForm C, indicating no form conversion had occurred during the analysis.

A competitive slurry of Forms A, B, C and D in THF revealed that alongwith the other starting forms, Form C will also convert to the moststable anhydrate form (Form E) (see FIG. 6). Slurries comprising FormsA, C, D and E in water showed conversion to Form F after one week ofequilibration (Table 2). These findings indicate that Form F is morestable in water than Forms A, C, D and E. Form C was also observed toconvert to a mixture of Forms B and F by XRPD after an overnight slurryin water at ambient conditions. As a result, the aqueous solubility ofForm C was not determined.

Form C was observed to be stable after one week of storage at 60° C.HPLC and XRPD analysis of the thermally stressed material showed nosignificant degradation or signs of form conversion (Table 3). After twoweeks of storage at elevated relative humidity (88% RH), Form C wasconfirmed to be stable by XRPD and showed no indication of deliquescence(Table 4).

Brimonidine Pamoate Form D

Form D was observed from crystallizations of Form A in the followingbinary solvent systems, using fast-cooling profiles: NMP/MeCN(acetonitrile), DMSO/EtOH and DMSO/toluene. Form D was also isolatedfrom slow-cooling crystallizations such as: NMP/MeCN and NMP/IPA. Form Dwas fully characterized as described below.

Lots SUC-I-133(35) and SUC-I-133(7) obtained from a fast-coolingcrystallizations of Form A in DMSO/toluene and NMP/MeCN, afforded aunique crystalline XRPD pattern compared to the diffraction patterns ofForms A, B, C, E and F. FIG. 17 shows an XRPD spectrum of Form D (lotSUC-I-133(35)).

In one aspect, the present invention provides brimonidine pamoatepolymorph Form D characterized by an XRPD spectrum that comprises peaksat 2θ angles of 7.5, 12.8, 24.5, and 27.1°±0.2°.

In another aspect, the present invention provides brimonidine pamoatepolymorph Form D characterized by an XRPD spectrum that comprises peaksat 2θ angles of 7.5, 11.1, 12.8, 18.4, 19.4, 22.5, 23.1, 24.5, 16.4, and27.1°±0.2°.

¹H NMR analysis of Form D, lot SUC-I-133(35), showed a 0.5:1 pamoate tobrimonidine ratio confirming the formation of a hemi-pamoate salt ofbrimonidine. FIG. 18 shows an NMR spectrum for brimonidine pamoatepolymorph Form D (lot SUC-I-133 (35)).

Thermal analysis of Form D, lot SUC-I-133(7), by DSC showed endothermicevents at 50 and 206° C. (see FIG. 19) attributed to a loss of residualsolvent and melting of the crystalline salt. Further analysis of lotSUC-I-133(35) by TGA showed no weight loss below 160° C. (see FIG. 20).

FIG. 21 shows a Raman spectroscopy spectrum of Form D (lotSUC-I-134(7)).

In one aspect, the present invention provides brimonidine pamoatepolymorph Form D characterized by a Raman spectroscopy spectrum thatcomprises peaks at 157.4, 1270.4, 1341.5, 1355.5, and 1403.0 cm⁻¹.

In another aspect, the present invention provides brimonidine pamoatepolymorph Form D characterized by a Raman spectroscopy spectrum thatcomprises peaks at 135.7, 146.8, 157.4, 188.9, 328.8, 429.0, 548.8,720.2, 1030.8, 1253.6, 1270.4, 1341.5, 1355.5, 1403.0, 1461.3, 1549.8,and 1572.6 cm⁻¹.

Raman spectroscopy analysis of Form D showed minor spectral differencesin comparison to the Raman spectra of Form A, C, and E, but significantdifferences in comparison to the spectra of Forms B and F in the rangeof about 1300-1425 cm⁻¹.

Moisture sorption analysis of lot SUC-I-133(7) showed Form D to beslightly hygroscopic, adsorbing 1.8 wt % water at 60% RH and 2.6 wt %water at 90% RH. Upon desorption no hysteresis or indication of hydrateformation was observed. XRPD analysis of the solids following moisturesorption analysis afforded a diffraction pattern which was consistentwith Form D, indicating no form conversion had occurred during theexperiment.

A competitive slurry of Forms A, B, C and D in THF revealed that alongwith the other starting forms, Form D will also convert to the moststable anhydrate form (Form E) (see FIG. 6). Slurries comprising FormsA, C, D and E in water showed conversion to Form F after one week ofequilibration (Table 2). These findings indicate that Form F is morestable in water than Forms A, C, D and E. Form D was also observed toconvert to a mixture of Forms B and F by XRPD after an overnight slurryin water at ambient conditions. As a result, the aqueous solubility ofForm D was not determined.

Form D was observed to be stable after one week of storage at 60° C.HPLC and XRPD analysis of the thermally stressed material showed nosignificant degradation or signs of form conversion (Table 3).

Brimonidine Pamoate Polymorph Form E

Form E was observed from a one week of slurry of Form A in THF, andlater obtained from larger scale slurry of Form A after 18 days.

Form E, lot SUC-I-132(2), afforded a unique crystalline XRPD patterncompared to the diffraction patterns of Forms A, B, C, D and F. FIG. 22shows an XRPD spectrum of Form E (lot SUC-I-132(2)).

In one aspect, the present invention provides brimonidine pamoatepolymorph Form E characterized by an XRPD spectrum that comprises peaksat 2θ angles of 7.7, 8.0, 13.1, and 21.2°±0.2°.

In another aspect, the present invention provides brimonidine pamoatepolymorph Form E characterized by an XRPD spectrum that comprises peaksat 2θ angles of 7.7, 8.0, 13.1, and 21.2°±0.2°.

¹H NMR analysis showed a 0.5:1 pamoate to brimonidine ratio confirmingthe formation of a hemi-pamoate salt of brimonidine which containedapproximately 0.2 wt % and 0.3 wt % residual THF and EtOH respectively.FIG. 23 shows an NMR spectrum for brimonidine pamoate polymorph Form E(lot SUC-I-132(2)).

Thermal analysis of Form E showed DSC endothermic events around 71° C.attributed to loss of residual solvent and at 207° C. (see FIG. 24) dueto melting of the crystalline salt. Further analysis by TGA showed a3.7% weight loss between 50 and 150° C. (see FIG. 25) likely attributedto loss of residual THF, EtOH and water.

FIG. 26 shows a Raman spectroscopy spectrum of Form E (lotSUC-I-132(2)).

In one aspect, the present invention provides brimonidine pamoatepolymorph Form E characterized by a Raman spectroscopy spectrum thatcomprises peaks at 1339.9, 1368.7, 1396.1, 1403.1, and 1410.8 cm⁻¹.

In another aspect, the present invention provides brimonidine pamoatepolymorph Form E characterized by a Raman spectroscopy spectrum thatcomprises peaks at 326.5, 466.6, 549.8, 720.5, 1030.3, 1270.4, 1339.9,1368.7, 1396.1, 1403.1, 1410.8, 1460.8, and 1573.7 cm⁻¹.

Raman spectroscopy analysis of Form E showed minor spectral differencesin comparison to the Raman spectra of Forms A, C, and D, but significantdifferences in comparison to the spectra of Forms B and F in the rangeof about 1300-1425 cm⁻¹.

Moisture sorption analysis of lot SUC-I-138(2) showed Form E to beslightly hygroscopic adsorbing 3.1 wt % water at 60% RH and 4.2 wt %water at 90% RH. Upon desorption, no hysteresis or indication of hydrateformation was observed. XRPD analysis of the solids following moisturesorption analysis afforded a diffraction pattern which was consistentwith Form E, indicating no form conversion had occurred during theexperiment.

A competitive slurry of Forms A, B, C and D in THF revealed that eachform converted to the anhydrate Form E. These findings suggest that FormE is the most stable anhydrate form. A slurry comprising Forms A, C, Dand E in water showed conversion to Form F after one week ofequilibration (Table 2). These findings indicate that Form F is morestable in water than Forms A, C, D and E. Form E was observed to convertto a mixture of Forms B and F by XRPD after overnight slurry in water atambient conditions. As a result, the aqueous solubility of Form E wasnot determined.

Form E was observed to be stable after one week of storage at 60° C.HPLC and XRPD analysis of the thermally stressed material showed nosignificant degradation or signs of form conversion (Table 3).

Brimonidine Pamoate Polymorph Form F

Form F was observed from the following binary solvent crystallizationswhich utilized fast cooling profiles: NMP/water and DMSO/water. Thisunique solid form was characterized as described below.

Lots SUC-I-133(37) and SUC-I-133(38) obtained from crystallizations ofForm A in NMP/water and DMSO/water solvent systems, using fast-coolingprofile (as described herein above), afforded a unique crystalline XRPDpattern compared to the diffraction patterns of Forms A, C, D, and E.The diffraction pattern of Form F showed some similarities to that ofthe Form B sesqui-hydrate. FIG. 27 shows an XRPD spectrum of Form F (lotSUC-I-136(2)).

In one aspect, the present invention provides brimonidine pamoatepolymorph Form F characterized by an X-ray powder diffraction (“XRPD”)spectrum that comprises peaks at 28 angles of 7.1, 9.8, 17.8, and25.5°±0.2°.

In another aspect, the present invention provides brimonidine pamoatepolymorph Form F characterized by an X-ray powder diffraction (“XRPD”)spectrum that comprises peaks at 28 angles of 7.1, 9.8, 11.0, 14.1,17.8, 21.4, 23.7, 25.5, 26.6, 27.6, and 30.0°±0.2°.

A slurry comprising Forms A, C, D, and E in water showed conversion toForm F after one week of equilibration (see FIG. 6). These findingsindicate that Form F is more stable in water than Forms A, C, D, and E.A water slurry of Form F left overnight showed the presence of a mixtureof Forms B and F. Thus, Form B is the more stable form in water. Thiswas confirmed in subsequent repeated experiments.

¹H NMR analysis showed a 0.5:1 pamoate to brimonidine ratio, confirmingthe formation of a hemi-pamoate salt of brimonidine and approximately0.3 wt % residual DMF. FIG. 28 shows an NMR spectrum for brimonidinepamoate polymorph Form F (lot SUC-I-183(1)).

Thermal analysis by DSC showed multiple endothermic events at 68, 216,228 and 246° C. (see FIG. 29) attributed to loss of water and/or DMF andmelting of the crystalline salt. Further analysis of Form F by KF showedapproximately 6.2 wt % water and 4.0 wt % loss by TGA (see FIG. 30).

FIG. 31 shows a Raman spectroscopy spectrum of Form F (lotSUC-I-136(2)). This Raman spectrum shows some similarities to Form B(compare FIGS. 11 and 31).

In one aspect, the present invention provides brimonidine pamoatepolymorph Form F characterized by a Raman spectroscopy spectrum thatcomprises peaks at 145.1, 156.3, 1336.8, 1364.4, and 1412.5 cm⁻¹.

In another aspect, the present invention provides brimonidine pamoatepolymorph Form F characterized by a Raman spectroscopy spectrum thatcomprises peaks at 131.4, 145.1, 156.3, 176.6, 235.1, 431.2, 693.8,718.3, 1336.8, 1364.4, 1412.5, 1440.2, and 1461.7 cm⁻¹

Moisture sorption analysis of lot SUC-I-183(1) was performed to furtherconfirm the hydration state of Form F. Form F adsorbed approximately 1.8molar equivalent of water at 40% RH suggesting a di-hydrate ofbrimonidine hemi-pamoate. XRPD analysis of the solids following themoisture sorption analysis afforded a diffraction pattern which wasconsistent with Form F, indicating no form conversion had occurredduring the experiment.

In another aspect, the present invention provides a pharmaceuticalcomposition comprising a polymorph of brimonidine pamoate selected fromthe group consisting of polymorph Forms A, B, C, D, E, F, andcombinations thereof.

In still another aspect, the present invention provides a pharmaceuticalcomposition comprising a polymorph of brimonidine pamoate selected fromthe group consisting of polymorph Forms B, C, D, E, F, and combinationsthereof.

In one embodiment, such a pharmaceutical composition comprises anaqueous carrier.

In another embodiment, such a pharmaceutical composition comprises anorganic carrier, such as a hydrophobic or a hydrophilic organicmaterial.

In still another embodiment, the pharmaceutical composition comprisesbrimonidine pamoate polymorph Form B.

In yet another embodiment, the pharmaceutical composition comprisesbrimonidine pamoate polymorph Form E.

In a further embodiment, the pharmaceutical composition comprisesbrimonidine pamoate polymorph Form F.

In one aspect, a pharmaceutical composition comprising a polymorph ofbrimonidine pamoate selected from the group consisting of polymorphForms A, B, C, D, E, F, and combinations thereof is administered to asubject in need of treatment or control of glaucoma.

In another aspect, a pharmaceutical composition comprising a polymorphof brimonidine pamoate selected from the group consisting of polymorphForms B, C, D, E, F, and combinations thereof is administered to asubject in need of treatment or control of elevated intraocularpressure.

In still another aspect, the pharmaceutical composition can be used toprovide neuroprotection to cells and components of a nervous system. Inone embodiment, the nervous system comprises the optic nerve system.

A concentration of at least about 0.3 μg/ml of a brimonidine pamoatepolymorph near the site of the damaged tissue is believed adequately toprovide therapeutic value for neuroprotection.

In still another aspect, a brimonidine pamoate polymorph is present inthe composition in an amount in a range from about 0.0001 to about 95percent (weight by volume). As used herein, the phrase “1 percent(weight by volume),” for example, means 1 gram in 100 ml of thecomposition. In one embodiment, the brimonidine pamoate polymorph ispresent in the composition in an amount in a range from about 0.0005 toabout 75 percent (weight by volume), or alternatively, from about 0.001to about 50, or from about 0.001 to about 25, or from about 0.001 toabout 10, or from about 0.001 to about 5, or from about 0.001 to about1, or from about 0.001 to about 0.5, or from about 0.002 to about 0.2,or from about 0.005 to about 0.1 percent (weight by volume).

In yet another aspect, a brimonidine pamoate polymorph is present in thecomposition in an amount in a range from about 0.0001 to about 95percent (by weight of the total composition). In one embodiment, thebrimonidine pamoate polymorph is present in the composition in an amountin a range from about 0.0005 to about 75 percent by weight, oralternatively, from about 0.001 to about 50, or from about 0.001 toabout 25, or from about 0.001 to about 10, or from about 0.001 to about5, or from about 0.001 to about 1, or from about 0.001 to about 0.5, orfrom about 0.002 to about 0.2, or from about 0.005 to about 0.1 percentby weight.

In one embodiment, a composition of the present invention is in a formof a suspension or dispersion. In another embodiment, the suspension ordispersion is based on an aqueous solution. For example, a compositionof the present invention can comprise micrometer- or nanometer-sizedparticles of the complex suspended or dispersed in sterile salinesolution. In another embodiment, the suspension or dispersion is basedon a hydrophobic medium. For example, the micrometer- or nanometer-sizedparticles of the complex can be suspended in a hydrophobic solvent e.g.,silicone oil, mineral oil, or any other suitable nonaqueous medium fordelivery to the eye. In still another embodiment, the micrometer- ornanometer-sized particles of the complex can be coated with aphysiologically acceptable surfactant (non-limiting examples aredisclosed below), then the coated particles are dispersed in a liquidmedium. The coating can keep the particles in a suspension. Such aliquid medium can be selected to produce a sustained-release suspension.For example, the liquid medium can be one that is sparingly soluble inthe ocular environment into which the suspension is administered. Instill another embodiment, the complex is suspended or dispersed in ahydrophobic medium, such as an oil. In still another embodiment, such amedium comprises an emulsion of a hydrophobic material and water. Instill another embodiment, the insoluble complex disclosed herein can bedosed by any normal drug delivery vehicle including but not limited tosuspension in a liposome formulation (both within and outside theliposome wall or strictly outside the liposome core), in the continuousphase of an emulsion or microemulsion, in the oil phase of the emulsion,or in a micellar solution using either charged or uncharged surfactants.A micellar solution wherein the surfactant is both the micelle formingagent and the anion of the complex disclosed herein would be preferable.

In another aspect, a composition of the present invention can furthercomprise a non-ionic surfactant, such as polysorbates (such aspolysorbate 80 (polyoxyethylene sorbitan monooleate), polysorbate 60(polyoxyethylene sorbitan monostearate), polysorbate 20 (polyoxyethylenesorbitan monolaurate), commonly known by their trade names of Tween® 80,Tween® 60, Tween® 20), poloxamers (synthetic block polymers of ethyleneoxide and propylene oxide, such as those commonly known by their tradenames of Pluronic®; e.g., Pluronic® F127 or Pluronic® F108)), orpoloxamines (synthetic block polymers of ethylene oxide and propyleneoxide attached to ethylene diamine, such as those commonly known bytheir trade names of Tetronic®; e.g., Tetronic® 1508 or Tetronic® 908,etc., other nonionic surfactants such as Brij®, Myrj®, and long chainfatty alcohols (i.e., oleyl alcohol, stearyl alcohol, myristyl alcohol,docosohexanoyl alcohol, etc.) with carbon chains having about 12 or morecarbon atoms (e.g., such as from about 12 to about 24 carbon atoms).Such compounds are delineated in Martindale, 34^(th) ed., pp. 1411-1416(Martindale, “The Complete Drug Reference,” S. C. Sweetman (Ed.),Pharmaceutical Press, London, 2005) and in Remington, “The Science andPractice of Pharmacy,” 21^(st) Ed., p. 291 and the contents of chapter22, Lippincott Williams & Wilkins, New York, 2006). The concentration ofa non-ionic surfactant, when present, in a composition of the presentinvention can be in the range from about 0.001 to about 5 weight percent(or alternatively, from about 0.01 to about 4, or from about 0.01 toabout 2, or from about 0.01 to about 1, or from about 0.01 to about 0.5weight percent). Any of these surfactants also can be used to coatmicrometer- or nanometer-sized particles, as disclosed above.

In addition, a composition of the present invention can includeadditives such as buffers, diluents, carriers, adjuvants, or otherexcipients. Any pharmacologically acceptable buffer suitable forapplication to the eye may be used. Other agents may be employed in thecomposition for a variety of purposes. For example, buffering agents,preservatives, co-solvents, oils, humectants, emollients, stabilizers,or antioxidants may be employed.

Water-soluble preservatives which may be employed include sodiumbisulfite, sodium bisulfate, sodium thiosulfate, benzalkonium chloride,chlorobutanol, thimerosal, ethyl alcohol, methylparaben, polyvinylalcohol, benzyl alcohol, phenylethyl alcohol, peroxide (such as hydrogenperoxide, urea hydrogen peroxide, or a source that generate a peroxidecompound such as perborate), biguanide compounds, and quaterniumcompounds (such as polyquat-1, polyquat-10, etc.). These agents may bepresent in individual amounts of from about 0.001 to about 5 percent byweight (preferably, about 0.01 to about 2 percent by weight).

Suitable water-soluble buffering agents that may be employed are sodiumcarbonate, sodium borate, sodium phosphate, sodium acetate, sodiumbicarbonate, etc., as approved by the United States Food and DrugAdministration (“US FDA”) for the desired route of administration. Theseagents may be present in amounts sufficient to maintain a pH of thesystem of between about 5 and about 8. As such, the buffering agent maybe as much as about 5 percent on a weight to weight basis of the totalcomposition. Electrolytes such as, but not limited to, sodium chlorideand potassium chloride may also be included in the formulation.Physiologically acceptable buffers include, but are not limited to, aphosphate buffer or a Tris-HCl buffer (comprisingtris(hydroxymethyl)aminomethane and HCl). For example, a Tris-HCl bufferhaving pH of 7.4 comprises 3 g/l of tris(hydroxymethyl)aminomethane and0.76 g/l of HCl. In yet another aspect, the buffer is 10× phosphatebuffer saline (“PBS”) or 5×PBS solution.

Other buffers also may be found suitable or desirable in somecircumstances, such as buffers based on HEPES(N-{2-hydroxyethyl}piperazine-N′-{2-ethanesulfonic acid}) having pK_(a)of 7.5 at 25° C. and pH in the range of about 6.8-8.2; BES(N,N-bis{2-hydroxyethyl}2-aminoethanesulfonic acid) having pK_(a) of 7.1at 25° C. and pH in the range of about 6.4-7.8; MOPS(3-{N-morpholino}propanesulfonic acid) having pK_(a) of 7.2 at 25° C.and pH in the range of about 6.5-7.9; TES(N-tris{hydroxymethyl}-methyl-2-aminoethanesulfonic acid) having pK_(a)of 7.4 at 25° C. and pH in the range of about 6.8-8.2; MOBS(4-{N-morpholino}butanesulfonic acid) having pK_(a) of 7.6 at 25° C. andpH in the range of about 6.9-8.3; DIPSO(3-(N,N-bis{2-hydroxyethyl}amino)-2-hydroxypropane)) having pK_(a) of7.52 at 25° C. and pH in the range of about 7-8.2; TAPSO(2-hydroxy-3{tris(hydroxymethyl)methylamino}-1-propanesulfonic acid))having pK_(a) of 7.61 at 25° C. and pH in the range of about 7-8.2; TAPS({(2-hydroxy-1,1-bis(hydroxymethyl)ethyl)amino}-1-propanesulfonic acid))having pK_(a) of 8.4 at 25° C. and pH in the range of about 7.7-9.1;TABS (N-tris(hydroxymethyl)methyl-4-aminobutanesulfonic acid) havingpK_(a) of 8.9 at 25° C. and pH in the range of about 8.2-9.6;AMPSO(N-(1,1-dimethyl-2-hydroxyethyl)-3-amino-2-hydroxypropanesulfonicacid)) having pK_(a) of 9.0 at 25° C. and pH in the range of about8.3-9.7; CHES (2-cyclohexylamino)ethanesulfonic acid) having pK_(a) of9.5 at 25° C. and pH in the range of about 8.6-10.0; CAPSO(3-(cyclohexylamino)-2-hydroxy-1-propanesulfonic acid) having pK_(a) of9.6 at 25° C. and pH in the range of about 8.9-10.3; or CAPS(3-(cyclohexylamino)-1-propane sulfonic acid) having pK_(a) of 10.4 at25° C. and pH in the range of about 9.7-11.1.

In one aspect, the composition has a pH that is suitable foradministration into a subject; e.g., to render the compositionnon-irritating. For example, for topical ophthalmic administration, adesired pH is in the range from about 5 to about 8.

In one aspect, the composition has a pH of about 7. Alternatively, thecomposition has a pH in a range from about 7 to about 7.5.

In another aspect, the composition has a pH of about 7.4.

In yet another aspect, a composition also can comprise aviscosity-modifying compound designed to facilitate the administrationof the composition into the subject or to promote the bioavailability inthe subject. In still another aspect, the viscosity-modifying compoundmay be chosen so that the composition is not readily dispersed afterbeing administered into an ocular environment (such as the ocularsurface, conjunctiva, or vitreous). Such compounds may enhance theviscosity of the composition, and include, but are not limited to:monomeric polyols, such as, glycerol, propylene glycol, ethylene glycol;polymeric polyols, such as, polyethylene glycol; various polymers of thecellulose family, such as hydroxypropylmethyl cellulose (“HPMC”),carboxymethyl cellulose (“CMC”) sodium, hydroxypropyl cellulose (“HPC”);polysaccharides, such as hyaluronic acid and its salts, chondroitinsulfate and its salts, dextrans, such as, dextran 70; water solubleproteins, such as gelatin; vinyl polymers, such as, polyvinyl alcohol,polyvinylpyrrolidone, povidone; carbomers, such as carbomer 934P,carbomer 941, carbomer 940, or carbomer 974P; and acrylic acid polymers.In general, a desired viscosity can be in the range from about 1 toabout 400 centipoises (“cp” or mPa·s).

In another aspect, the present invention provides a method for producinga composition comprising a brimonidine pamoate polymorph selected fromthe group consisting of polymorph Forms A, B, C, D, E, F, andcombinations thereof (or alternatively, polymorph Forms B, C, D, E, F,and combinations thereof), the method comprising: (a) providing saidbrimonidine pamoate polymorph; and (b) dispersing an amount of saidpolymorph in a sufficient amount of said medium to produce saidcomposition to achieve a predetermined concentration of said polymorphin said medium. Alternatively, a portion of the polymorph remains in asolid phase for a period longer than 2 days, or 1 week, or 1 month, or 2months, or 3 months, or 4 months, or 5 months, or 6 months, or 1 year,or 2 years after said polymorph has been in contact with said medium. Inone embodiment, the method can optionally include a step of reducing thesize of the polymorph before dispersing such polymorph in the medium.

In still another aspect, the present invention provides a method forproducing brimonidine pamoate polymorph Form B or F. The methodcomprises: (a) producing brimonidine pamoate polymorph Form A; (b)contacting said polymorph Form A with water for a time sufficient toconvert said polymorph Form A to polymorph Form B or F.

In still another aspect, the present invention provides a method forproducing brimonidine pamoate polymorph Form B or F. The methodcomprises: (a) producing brimonidine pamoate polymorph Form A, C, D, E,or a combination thereof; (b) contacting said polymorph Form A, C, D, E,or combination thereof with water for a time sufficient to convert saidpolymorph Form A, C, D, E, or combination thereof to polymorph Form B orF.

In yet another aspect, the present invention provides a method forproducing brimonidine pamoate polymorph Form E. The method comprises:(a) producing brimonidine pamoate polymorph Form A; (b) contacting saidpolymorph Form A with THF for a time sufficient to convert saidpolymorph Form A to polymorph Form E.

In a further aspect, the present invention provides a method forproducing brimonidine pamoate polymorph Form E. The method comprises:(a) producing brimonidine pamoate polymorph Form A, B, C, D, or acombination thereof; (b) contacting said polymorph Form A, B, C, D, orcombination thereof with THF for a time sufficient to convert saidpolymorph Form A, B, C, D, or combination thereof to polymorph Form E.

In another aspect, a formulation comprising a brimonidine pamoatepolymorph selected from the group consisting of polymorph Forms A, B, C,D, E, F, and combinations thereof (or alternatively, polymorph Forms B,C, D, E, F, and combinations thereof) is prepared for topicaladministration, periocular injection, or intravitreal injection. Aninjectable intravitreal formulation can desirably comprise a carrierthat provides a sustained-release of the active ingredients, such as fora period longer than about one day, or one week, or longer than about 1,2, 3, 4, 5, or 6 months, or 1 or 2 years. In certain embodiments, thesustained-release formulation desirably comprises a carrier that isinsoluble or only sparingly soluble in an ocular environment (such asthe ocular surface, conjunctiva, or vitreous). Such a carrier can be anoil-based liquid, emulsion, gel, or semisolid. Non-limiting examples ofoil-based liquids include castor oil, peanut oil, olive oil, coconutoil, sesame oil, cottonseed oil, corn oil, sunflower oil, fish-liveroil, arachis oil, and liquid paraffin.

In one aspect, a composition of the present invention can beadministered into a subject in need of neuroprotection at one time orover a series of treatments. A composition of the present invention maybe administered locally; e.g., intravitreally by intrabulbar injectionfor ocular neuroprotection, or by intrathecal or epidural administrationfor spinal protection. Many of the compositions of the invention can beadministered systemically; e.g., orally, or intravenously, or byintramuscular injection. In addition, compositions for protection of theretina and optic nerve that are capable of passing through the corneaand achieving sufficient concentration in the vitreous humor (such as aconcentration disclosed herein above) may also be administered topicallyto the eye. In one embodiment, the neuroprotection can preventprogressive damage to cells or components of the optic nerve, whichdamage results from glaucoma, retinitis pigmentosa, AMD, diabeticretinopathy, diabetic macular edema, or other back-of-the-eye diseases.

In one embodiment, a composition of the present invention can beinjected intravitreally, for example through the pars plana of theciliary body, to treat or prevent glaucoma or progression thereof, or toprovide neuroprotection to the optic nerve system, using a fine-gaugeneedle, such as 25-30 gauge. Typically, an amount from about 25 μl toabout 100 μl of a composition comprising a brimonidine pamoate polymorphdisclosed herein is administered into a patient. A concentration of sucha polymorph is selected from the ranges disclosed above.

In still another aspect, a brimonidine pamoate polymorph selected fromthe group consisting of polymorph Forms A, B, C, D, E, F, andcombinations thereof (or alternatively, polymorph Forms B, C, D, E, F,and combinations thereof) is incorporated into an ophthalmic device orsystem that comprises a biodegradable material, and the device isinjected or implanted into a subject to provide a long-term (e.g.,longer than about 1 week, or longer than about 1, 2, 3, 4, 5, or 6months, or 1 or 2 years) treatment or prevention of glaucoma orprogression thereof, or to provide neuroprotection to the optic nervesystem. In some embodiments, the ophthalmic device or system cancomprise a semipermeable membrane that allows the complex to diffusetherethrough at a controlled rate. In still some other embodiments, sucha controlled rate provides a supply of the complex over an extendedperiod of time at or near the site of desired treatment. Such a devicesystem may be injected or implanted by a skilled physician in thesubject's ocular or periocular tissue.

Some compositions of the present invention are disclosed in the examplesbelow. It should be understood that the proportions of the listedingredients may be adjusted for specific circumstances.

Example 1

TABLE 1 Ingredient Amount Carbopol 934P NF 0.25 g Purified water 99.75 gPropylene glycol 5 g EDTA 0.1 mg Brimonidine pamoate polymorph Form B100 mg

An appropriate proportion of EDTA (e.g., shown in Table 1) is added topurified water in a stainless steel jacketed vessel that is equippedwith a stirring mechanism. An appropriate amount of carbopol 934P NF isadded, over a period of five to ten minutes to form a substantiallyuniform dispersion. Propylene glycol is added to the resulting mixturewhile mixing for three to ten minutes. Then, an appropriate amount tobrimonidine pamoate having polymorph Form B, which may be previouslymicronized, is added to the contents of the vessel over a period ofthree to five minutes while mixing continues until the compound issubstantially dispersed. The pH of the mixture is adjusted to 7-7.5using 1 N NaOH or 1 N HCL solution. The final composition is sterilized,using, for example, heat or radiation and then packaged in appropriatecontainers.

Example 2

A procedure similar to that disclosed in Example 1 is used to producethe composition of the present invention having the ingredients listedin Table 2.

TABLE 2 Amount (% by weight, except Ingredient where “ppm” is indicated)Povidone 1.5 HAP (30%) 0.05 Glycerin 3 Propylene glycol 3 Brimonidinepamoate polymorph Form F 0.5 Alexidine 2HCl 1-2 ppm Purified water q.s.to 100 Note: “HAP” denotes hydroxyalkyl phosphonates, such as thoseknown under the trade name Dequest ®. HAPs can be used as chelatingagents and have been shown to inhibit bacterial and fungal cellreplication.

Example 3

A procedure similar to that disclosed in Example 1 is used to producethe composition of the present invention having the ingredients listedin Table 3.

TABLE 3 Amount (% by weight, except Ingredient where “ppm” is indicated)Glycerin 3 Propylene glycol 3 Brimonidine pamoate polymorph Form E 0.25Alexidine 1-2 ppm Sunflower oil q.s. to 100

Example 4

A modification of the procedure disclosed in Example 1 is used toproduce the composition of the present invention having the ingredientslisted in Table 4.

An appropriate proportion of polysorbate 80 (e.g., shown in Table 4) isadded to approximately 20 percent of the desired final volume ofpurified water in a stainless steel jacketed vessel that is equippedwith a stirring mechanism. Glycerin and propylene glycol are then addedto the mixture while mixing continues for five more minutes. To asterilized second vessel, heated to about 80° C. and equipped with astirring mechanism, containing approximately 70 percent of the desiredfinal volume of purified water, an appropriate amount of CMC-MV is addedover a period of three to five minutes while mixing continues until theCMC forms a substantially uniform solution. The contents of the secondvessel are cooled to about room temperature and then the contents of thefirst vessel are transferred into the second vessel. The remaining ofthe desired volume of purified water is added to the second vessel.Then, appropriate amounts of brimonidine pamoate polymorphs Form B andForm F are added to the contents of the second vessel over a period ofthree to five minutes while mixing continues until the drugs aresubstantially uniformly dispersed. The pH of the mixture is adjusted to7-7.5 using 1 N NaOH or 1 N HCl solution. The final composition issterilized, using, for example, heat or radiation, and packaged inappropriate containers.

TABLE 4 Amount (% by weight, except Ingredient where “ppm” is indicated)Carboxymethyl cellulose, medium 0.5 viscosity (“CMC-MV”) Glycerin 3Propylene glycol 3 Brimonidine pamoate polymorph Form B 0.3 Brimonidinepamoate polymorph Form F 0.3 Polysorbate 80 ® (a surfactant) 0.25Alexidine 2HCl 1-2 ppm Purified water q.s. to 100

Example 5

A procedure similar to that of Example 1 is used to produce acomposition comprising the ingredients listed in Table 5.

TABLE 5 Amount (% by weight, except Ingredient where “ppm” is indicated)Glycerin 3 Propylene glycol 3 Brimonidine pamoate polymorph Form E 0.5Tween ® 80 0.25 Alexidine 1-2 ppm Corn oil q.s. to 100

Example 6

A procedure similar to that of Example 4 is used to produce acomposition comprising the ingredients listed in Table 6.

TABLE 6 Amount (% by weight, except Ingredient where “ppm” is indicated)CMC (MV) 0.5 Glycerin 3 Propylene glycol 3 Brimonidine pamoate polymorphForm B 0.75 Brimonidine pamoate polymorph Form A 0.75 Tyloxapol (asurfactant) 0.25 Alexidine 2HCl 1-2 ppm Purified water q.s. to 100

Example 7

A procedure similar to that of Example 1 is used to produce acomposition comprising the ingredients listed in Table 7.

TABLE 7 Amount (% by weight, except Ingredient where “ppm” is indicated)HPMC 0.5 Glycerin 3 Propylene glycol 3 Brimonidine pamoate polymorphForm A 0.6 Brimonidine pamoate polymorph Form C 0.6 Brimonidine pamoatepolymorph Form D 0.6 Tyloxapol (a surfactant) 0.25 Alexidine 2HCl 1-2ppm Purified water q.s. to 100

Alternatively, purified water may be substituted with an oil, such asfish-liver oil, peanut oil, sesame oil, coconut oil, sunflower oil, cornoil, or olive oil to produce an oil-based formulation comprising abrimonidine pamoate polymorph.

Benefits of brimonidine pamoate polymorphs, or compositions comprisingthe same, of the present invention for neuroprotection can bedetermined, judged, estimated, or inferred by conducting assays andmeasurements, for example, to determine: (1) the protection of nervecells from glutamate induced toxicity; and/or (2) the neural protectionin a nerve crush model of mechanical injury. Non-limiting examples ofsuch assays and measurements are disclosed in U.S. Pat. No. 6,194,415,which is incorporated herein by reference.

The following sections disclose the instrumentation and procedures usedin applicable experiments disclosed hereinabove.

Instrumentation

Instrument Name and Model Number Differential Scanning CalorimeterMettler 822^(e) DSC Thermal Gravimetric Analyzer Mettler 851^(e)SDTA/TGA X-Ray Powder Diffraction System Shimadzu XRD-6000Moisture-Sorption Analysis IGAsorp Moisture Sorption Instrument NuclearMagnetic Resonance 500 MHz Broker AVANCE Spectrometer High-PerformanceLiquid Waters Alliance Chromatography Raman Spectrometer Kaiser RXN1Differential Scanning calorimetry

Differential scanning calorimetry (“DSC”) analyses were carried out onthe samples “as is”. Samples were weighed in an aluminum pan, coveredwith a pierced lid, and then crimped. Analysis conditions were 30° C. to30-300 or 350° C. ramped at 10° C./minute.

Thermal Gravimetric Analysis

Thermal gravimetric analysis (“TGA”) analyses were carried out on thesamples “as is”. Samples were weighed in an alumina crucible andanalyzed from 30° C. to 230° C. at 10° C./minute.

X-Ray Powder Diffraction

Samples for x-ray powder diffraction (“XRPD”) were analyzed “as is”.Samples were placed on Si zero-return ultra-micro sample holders andanalyzed using the following conditions:

X-ray tube: Cu Kα, 40 kV, 30 mA Slits Divergence Slit 1.00 deg ScatterSlit 1.00 deg Receiving Slit 0.30 mm Scanning Scan Range 3.0-45.0 degScan Mode Continuous Step Size 0.04° Scan Rate 2°/minute

Moisture Sorption Analysis

Moisture sorption analysis was performed on brimonidine hemi-pamoatestarting material at 25° C. from 40 to 90% relative humidity (“RH”) forthe adsorption scan, from 85 to 0% RH from the desorption scan and 10 to40% RH to complete the adsorption scan. Approximately 10 mg of thesample was analyzed in a Pyrex bulb. Each scan utilized a step size of10% RH and a maximum equilibration time of four hours per point. Thesample was dried for one hour at 80° C. following the desorption scan toobtain the dry sample weight and then it was analyzed by XRPD.

Nuclear Magnetic Resonance

Samples (˜2 to 10 mg) of brimonidine hemi-pamoate were dissolved inDMSO-d₆ with 0.05% tetramethylsilane (“TMS”) for internal reference. ¹HNMR spectra were acquired at 500 MHz using 5 mm broadband observe (¹H—X)Z gradient probe. A 30 degree pulse with 20 ppm spectral width, 1.0 srepetition rate, and 16 to 128 transients were utilized in acquiring thespectra.

High Performance Liquid Chromatography Instrument Parameters: Column:Agilent Eclipse XDB-C18, 4.6×150 mm

Mobile Phase A: 0.05% TFA in water

Mobile Phase B: 0.05% TFA in MeCN

Flow Rate: 1.0 mL/min

Column Temperature Ambient Detection: 248 nm Diluent: MeOH InjectionVolume: 5 μl

Gradient Conditions Time (minutes) % A % B 0 90 10 10 80 20 15 10 90 2290 10

Raman Spectroscopy

Samples for Raman spectroscopy analysis were analyzed “as is”. Sampleswere placed in a 96 well plate and analyzed using the followingconditions:

Raman Source: 785 nm laser Objective: 1.2 mm PHaT Single Exposure Time:12 seconds Co-Additions: 12 Enabled Exposure Options: Cosmic Rayfiltering Dark Subtraction Intensity Calibration

Peak Data List for FIG. 1.

Peak Data List 2Theta d I FWHM integrated I No. (degrees) (A) (counts)I/Io (degrees) (counts) 1 4.2466 20.79077 187 18 0.2185 1121 2 7.604611.61596 306 29 0.2754 2445 3 7.9817 11.06798 92 9 0.2701 645 4 8.478010.42114 49 5 0.2132 287 5 10.2865 8.59267 71 7 0.2589 516 6 10.64008.30797 50 5 0.3288 568 7 12.2376 7.22673 310 29 0.2694 2347 8 12.65516.98924 370 35 0.2541 2532 9 13.5142 6.54680 708 67 0.2539 5267 1015.9242 5.56101 407 39 0.2813 3253 11 17.2082 5.14885 95 9 0.2814 759 1217.5600 5.04649 69 7 0.2200 432 13 17.9600 4.93498 56 5 0.2172 304 1418.2926 4.84600 82 8 0.3587 798 15 19.0500 4.65500 46 4 0.2200 337 1620.5858 4.31105 536 51 0.3056 4728 17 21.1359 4.20007 1054 100 0.31478574 18 21.6400 4.10336 61 6 0.2400 656 19 22.3600 3.97283 53 5 0.1530195 20 22.6778 3.91787 184 17 0.3008 1664 21 23.7822 3.73837 180 170.2685 1282 22 24.3653 3.65021 465 44 0.4763 5402 23 25.2130 3.52937 797 0.3140 668 24 25.7958 3.45094 80 8 0.2583 533 25 26.5170 3.35870 33932 0.2629 2795 26 26.9200 3.30933 94 9 0.0000 0 27 27.1600 3.28062 100 90.0000 0 28 27.6643 3.22196 312 30 0.4589 3993 29 28.3600 3.14448 65 60.1930 466 30 29.0700 3.06927 143 14 0.3480 1289 31 29.7594 2.99972 10610 0.4469 1420 32 31.4704 2.84042 147 14 0.2799 1309 33 31.8800 2.8048646 4 0.0000 0 34 32.1600 2.78107 72 7 0.2934 648 35 33.1200 2.70262 45 40.4960 606 36 33.5373 2.66994 82 8 0.3253 653 37 34.1811 2.62111 78 70.4378 800 38 34.5200 2.59615 40 4 0.2400 340 39 36.0203 2.49138 44 40.5860 625 40 36.6483 2.45012 37 4 0.4033 315 41 37.4400 2.40011 54 50.2156 476 42 37.6800 2.38537 50 5 0.0000 0 43 38.0000 2.36602 43 40.0000 0 44 38.2000 2.35409 35 3 0.4000 291 45 38.5600 2.33294 33 30.8444 427 46 39.5569 2.27641 43 4 0.2088 237 47 40.1748 2.24281 88 80.2845 753 48 40.8706 2.20622 42 4 0.1922 236 49 41.1614 2.19130 44 40.2229 259 50 41.5793 2.17024 32 3 0.1925 184

Peak Data List for FIG. 7

Peak Data List 2Theta d I FWHM integrated I No. (degrees) (A) (counts)I/Io (degrees) (counts) 1 3.1200 28.29512 60 5 0.0960 176 2 6.640013.30110 77 7 0.1214 486 3 6.9590 12.69208 346 31 0.2045 1993 4 9.24009.56338 40 4 0.1334 331 5 9.6919 9.11846 1125 100 0.1549 5388 6 10.08008.76824 64 6 0.0972 469 7 10.9152 8.09912 328 29 0.1651 1745 8 11.20007.89380 43 4 0.1500 350 9 12.8400 6.88901 45 4 0.2666 407 10 13.06466.77108 112 10 0.1853 481 11 13.9829 6.32839 133 12 0.2059 900 1214.6097 6.05827 464 41 0.2178 2875 13 15.8563 5.58467 115 10 0.1547 67814 16.3336 5.42253 210 19 0.2007 1304 15 16.9123 5.23827 40 4 0.1398 22716 17.7200 5.00128 137 12 0.1692 693 17 17.9200 4.94591 168 15 0.1926807 18 18.4065 4.81627 78 7 0.1570 399 19 19.0254 4.66096 347 31 0.15791626 20 19.4563 4.55870 172 15 0.1734 856 21 20.1020 4.41370 309 270.1757 1429 22 20.4080 4.34821 68 6 0.2240 415 23 20.7623 4.27480 153 140.1809 711 24 21.0242 4.22214 183 16 0.1742 949 25 21.9600 4.04428 12211 0.1724 647 26 22.1600 4.00823 204 18 0.1576 817 27 22.4400 3.95885 696 0.1472 367 28 23.3503 3.80653 386 34 0.1740 1895 29 24.0046 3.70424 918 0.1416 432 30 25.0920 3.54612 219 19 0.1582 1114 31 25.4804 3.49294122 11 0.1325 429 32 25.9362 3.43258 437 39 0.1842 2312 33 26.46323.36540 364 32 0.2195 2126 34 26.8834 3.31375 185 16 0.2629 1292 3527.4400 3.24778 63 6 0.0868 201 36 27.6748 3.22076 312 28 0.1980 2113 3727.9600 3.18855 167 15 0.0000 0 38 28.2000 3.16196 86 8 0.1600 1020 3928.8839 3.08863 136 12 0.1444 489 40 29.1200 3.06412 93 8 0.1790 571 4129.8002 2.99571 36 3 0.2075 277 42 30.2953 2.94787 176 16 0.2227 1128 4331.0177 2.88084 56 5 0.1511 254 44 31.8400 2.80829 76 7 0.1544 462 4532.0919 2.78682 105 9 0.2202 638 46 32.7087 2.73566 43 4 0.1375 260 4734.4000 2.60493 34 3 0.1400 318 48 36.0075 2.49224 71 6 0.1650 510 4936.3455 2.46984 53 5 0.1257 223 50 36.8388 2.43789 59 5 0.1483 269

Peak Data List for FIG. 12

Peak Data List 2Theta d I FWHM integrated I No. (degrees) (A) (counts)I/Io (degrees) (counts) 1 3.1600 27.93705 12 4 0.0400 12 2 3.422025.79866 39 12 0.1025 103 3 3.7040 23.83511 88 27 0.2962 670 4 4.840018.24300 10 3 0.0572 13 5 6.6933 13.19530 14 4 0.1067 46 6 7.120012.40544 23 7 0.1236 122 7 7.3600 12.00144 50 16 0.2000 289 8 7.658211.53478 218 68 0.2728 1412 9 8.4163 10.49740 32 10 0.2073 216 10 9.26509.53763 13 4 0.1700 79 11 9.6339 9.17323 12 4 0.1835 94 12 11.13237.94165 59 18 0.3446 617 13 11.9947 7.37253 63 20 0.2106 478 14 12.83516.89163 321 100 0.2454 2388 15 13.4414 6.58210 203 63 0.3724 2174 1613.9943 6.32327 45 14 0.2114 284 17 14.3866 6.15171 10 3 0.1467 41 1814.9013 5.94036 31 10 0.2712 230 19 15.4581 5.72762 71 22 0.3438 633 2015.9600 5.54862 53 17 0.3134 506 21 16.9566 5.22468 39 12 0.1721 218 2218.3959 4.81902 171 53 0.2237 1257 23 19.1563 4.62941 109 34 0.2102 72524 19.8131 4.47740 117 36 0.2315 796 25 20.5843 4.31136 10 3 0.0886 4826 20.9200 4.24293 15 5 0.1900 91 27 21.3600 4.15651 88 27 0.3658 577 2821.6000 4.11087 48 15 0.5120 430 29 22.1600 4.00823 30 9 0.3200 282 3022.6435 3.92373 121 38 0.2281 746 31 23.0400 3.85709 15 5 0.1226 144 3223.4800 3.78580 41 13 0.1090 133 33 23.7994 3.73571 216 67 0.2887 171134 24.4000 3.64510 41 13 0.2934 455 35 25.0440 3.55281 37 12 0.2480 26236 25.8800 3.43991 42 13 0.1280 277 37 26.4800 3.36331 41 13 0.0000 0 3827.0221 3.29705 82 26 0.2708 1269 39 27.4800 3.24315 62 19 0.0000 0 4027.7600 3.21107 34 11 0.4228 493 41 28.3200 3.14883 35 11 0.2312 166 4228.5200 3.12720 39 12 0.2488 228 43 28.9543 3.08128 16 5 0.2286 95 4429.3227 3.04340 63 20 0.3196 528 45 30.2600 2.95123 26 8 0.2000 159 4630.5457 2.92427 10 3 0.1314 29 47 30.8000 2.90071 15 5 0.0700 24 4831.0600 2.87701 22 7 0.3600 206 49 31.4413 2.84299 14 4 0.1093 46 5032.0800 2.78783 28 9 0.1334 125Peak data List for FIG. 17

Peak Data List 2Theta d I FWHM integrated I No. (degrees) (A) (counts)I/Io (degrees) (counts) 1 7.0800 12.47543 14 7 0.1600 119 2 7.547111.70433 212 100 0.3942 2076 3 8.5000 10.39422 6 3 0.2000 29 4 10.30008.58144 8 4 0.2000 45 5 11.1091 7.95819 65 31 0.4000 679 6 12.08007.32066 22 10 0.2666 249 7 12.7821 6.92008 142 67 0.5108 1870 8 13.32006.64181 26 12 0.2000 221 9 14.0223 6.31070 27 13 0.4126 301 10 15.30385.78502 40 19 0.3790 367 11 15.9720 5.54447 22 10 0.3760 215 12 16.79065.27596 8 4 0.2053 45 13 17.5441 5.05102 16 8 0.3783 144 14 18.44254.80695 67 32 0.4050 727 15 19.3884 4.57451 95 45 0.4854 1168 16 19.92004.45362 21 10 0.3000 221 17 20.8733 4.25232 23 11 0.7067 437 18 21.92004.05157 40 19 0.6400 997 19 22.4800 3.95190 63 30 0.0000 0 20 23.08003.85050 75 35 0.6080 1572 21 24.5139 3.62842 145 68 0.7536 2918 2225.7200 3.46094 56 26 0.3854 641 23 26.4400 3.36830 71 33 0.6000 1054 2427.1018 3.28754 147 69 0.9236 2866 25 28.6586 3.11239 49 23 0.6507 84226 29.5960 3.01591 14 7 0.4720 143 27 29.9200 2.98399 7 3 0.2400 51 2830.6800 2.91178 11 5 0.4000 126 29 32.3200 2.76767 21 10 0.4480 194 3032.6800 2.73800 25 12 0.7466 350 31 33.2000 2.69629 7 3 0.0000 0 3236.0700 2.48807 15 7 0.4200 181 33 36.5600 2.45584 7 3 0.2000 62 3441.8000 2.15929 7 3 0.4000 89 35 43.2000 2.09250 6 3 0.2400 68

Peak Data List for FIG. 22

Peak Data List 2Theta d I FWHM integrated I No. (degrees) (A) (counts)I/Io (degrees) (counts) 1 3.6075 24.47248 26 6 0.1650 147 2 3.960022.29481 34 7 0.2134 165 3 4.3031 20.51791 80 18 0.3205 723 4 6.241414.14964 17 4 0.0611 38 5 7.2400 12.20009 36 8 0.2036 394 6 7.720011.44258 426 94 0.3118 3303 7 8.0000 11.04270 330 73 0.2948 2715 88.7200 10.13247 54 12 0.4266 848 9 9.6800 9.12964 14 3 0.2900 105 109.9628 8.87112 44 10 0.3257 342 11 11.0298 8.01522 57 13 0.3243 526 1212.3200 7.17858 51 11 0.2400 405 13 12.6400 6.99756 165 36 0.3244 156414 13.1212 6.74199 374 82 0.3888 3658 15 13.6800 6.46783 68 15 0.1688889 16 14.8000 5.98079 18 4 0.0000 0 17 15.3342 5.77362 60 13 0.3396 73418 15.9420 5.55484 40 9 0.2760 345 19 16.5868 5.34032 202 44 0.3160 170120 17.5000 5.06365 24 5 0.1400 105 21 18.0400 4.91328 141 31 0.2892 111122 18.4697 4.79993 188 41 0.3518 1617 23 19.4688 4.55580 165 36 0.32051292 24 19.9363 4.45001 70 15 0.2726 513 25 20.6000 4.30811 60 13 0.1792380 26 21.2273 4.18220 455 100 0.3783 4610 27 21.9152 4.05245 15 30.0526 39 28 22.6000 3.93118 119 26 0.2830 1096 29 23.2970 3.81512 28262 0.4626 3282 30 23.8977 3.72057 165 36 0.4917 1965 31 24.4800 3.6333789 20 0.3152 885 32 25.1600 3.53669 108 24 0.2244 662 33 25.4800 3.4929986 19 0.3032 1025 34 25.9600 3.42949 57 13 0.0000 0 35 26.6611 3.34087217 48 0.6191 3485 36 27.8800 3.19752 89 20 0.4492 976 37 28.24003.15757 123 27 0.2800 936 38 29.0688 3.06940 94 21 0.2546 702 39 29.56003.01950 57 13 0.1400 218 40 29.8400 2.99180 62 14 0.3074 607 41 31.12002.87160 48 11 0.4500 530 42 31.5126 2.83672 95 21 0.2739 584 43 31.92002.80144 49 11 0.2886 396 44 32.7342 2.73359 66 15 0.4432 626 45 33.20002.69629 53 12 0.2978 363 46 33.5500 2.66896 51 11 0.3572 422 47 34.26322.61502 25 5 0.1722 163 48 35.3161 2.53943 50 11 0.2477 265 49 35.53922.52400 50 11 0.1985 337 50 36.2800 2.47414 35 8 0.0800 163

Peak Data List for FIG. 27

Peak Data List 2Theta d I FWHM integrated I No. (degrees) (A) (counts)I/Io (degrees) (counts) 1 3.1200 28.29512 51 10 0.1458 205 2 3.555624.82958 38 7 0.0928 186 3 4.3943 20.09228 28 5 0.1014 143 4 4.795018.41411 31 6 0.0900 108 5 5.2227 16.90705 16 3 0.0879 43 6 6.680013.22154 74 14 0.1482 536 7 7.0596 12.51144 309 58 0.1992 1985 8 8.521110.36853 18 3 0.0577 43 9 8.9240 9.90130 16 3 0.0880 67 10 9.44009.36121 88 17 0.1866 782 11 9.7646 9.05073 532 100 0.2263 3059 1210.1600 8.69937 40 8 0.1908 525 13 10.6800 8.27695 38 7 0.1292 176 1411.0021 8.03534 226 42 0.2376 1509 15 11.3600 7.78298 26 5 0.1150 169 1613.0470 6.78017 93 17 0.2260 647 17 14.0525 6.29721 246 46 0.3632 243018 14.6791 6.02978 71 13 0.2258 452 19 15.5752 5.68482 50 9 0.3238 37320 15.9988 5.53525 64 12 0.2511 414 21 16.4000 5.40073 43 8 0.1666 20422 16.7463 5.28982 94 18 0.2474 621 23 17.7700 4.98732 270 51 0.25271705 24 18.1200 4.89177 89 17 0.3128 758 25 18.4843 4.79617 109 200.2930 804 26 19.0910 4.64510 34 6 0.1321 116 27 20.2740 4.37664 158 300.3763 1451 28 20.6400 4.29985 144 27 0.2316 710 29 21.0400 4.21900 13325 0.4290 1643 30 21.4400 4.14118 231 43 0.2254 1401 31 21.9901 4.0388237 7 0.2140 187 32 22.2000 4.00110 22 4 0.1600 120 33 22.6083 3.92976 377 0.1583 182 34 23.2000 3.83085 49 9 0.1800 331 35 23.6500 3.75897 23745 0.3000 1961 36 24.0000 3.70494 49 9 0.1494 328 37 24.5063 3.62953 306 0.1660 146 38 24.9600 3.56457 64 12 0.2742 540 39 25.5385 3.48512 26249 0.3049 1992 40 26.0000 3.42430 125 23 0.4572 1443 41 26.6124 3.34687221 42 0.3039 1600 42 26.9200 3.30933 71 13 0.2266 450 43 27.36003.25710 150 28 0.1894 671 44 27.5600 3.23391 167 31 0.3146 1087 4528.1427 3.16826 104 20 0.5040 1245 46 29.3165 3.04403 28 5 0.1989 191 4729.7200 3.00361 83 16 0.2000 497 48 30.0400 2.97234 177 33 0.2770 127049 30.4000 2.93795 92 17 0.2588 761 50 31.4461 2.84256 20 4 0.1477 154

While specific embodiments of the present invention have been describedin the foregoing, it will be appreciated by those skilled in the artthat many equivalents, modifications, substitutions, and variations maybe made thereto without departing from the spirit and scope of theinvention as defined in the appended claims.

1. (canceled)
 2. A brimonidine pamoate polymorph exhibiting a Ramanspectroscopy spectrum that comprises peaks at 145.1, 156.3, 1336.8,1364.4, and 1412.5 cm⁻¹. 3-27. (canceled)
 28. A composition comprising apharmaceutically acceptable carrier and a brimonidine pamoate polymorphof claim
 2. 29. The composition of claim 28, wherein thepharmaceutically acceptable carrier comprises an aqueous medium.
 30. Thecomposition of claim 28, wherein the pharmaceutically acceptable carriercomprises an organic medium.
 31. A method for providing neuroprotectionto a neurological tissue, said method comprising administering into asubject in need of such neuroprotection a composition of claim
 28. 32.The method of claim 31, wherein said neuroprotection preventsprogressive damage to cells or components of the optic nerve resultingfrom a back-of-the-eye pathological condition.
 33. The method of claim32, wherein said damage results from glaucoma, retinitis pigmentosa,AMD, diabetic retinopathy, diabetic macular edema, or combinationsthereof.
 34. The method of claim 31, wherein the method results inlowering intraocular pressure in said subject.
 35. A method forproducing a brimonidine pamoate polymorph of claim 2, the methodcomprising: (a) producing a precursor brimonidine pamoate polymorph thatexhibits exhibits an X-ray powder diffraction spectrum that comprisespeaks at 2θ angles of: (i) 13.5, 20.6, 21.1, and 24.4°±0.2°; (ii) 7.7,12.8, 13.4, and 23.8°±0.2°; (iii) 7.5, 12.8, 24.5, and 27.1°±0.2°; or(iv) 7.7, 8.0, 13.1, and 21.2°±0.2°; (b) contacting said precursorpolymorph with water for a time sufficient to convert said precursorpolymorph to the polymorph of claim 2.